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Abstract

Using a femtosecond laser writing technique, we fabricate and characterise three-waveguide digital adiabatic passage devices, with the central waveguide digitised into five discrete waveguidelets. Strongly asymmetric behaviour was observed, devices operated with high fidelity in the counter-intuitive scheme while strongly suppressing transmission in the intuitive. The low differential loss of the digital adiabatic passage designs potentially offers additional functionality for adiabatic passage based devices. These devices operate with a high contrast (>90%) over a 60 nm bandwidth, centered at ∼ 823 nm.

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

A. A. Rangelov and N. V. Vitanov, “Complete population transfer in a three-state quantum system by a train of pairs of coincident pulses,” Phys. Rev. A 85, 043407 (2012).
[Crossref]

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

Miese, C. T.

Milner, V.

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

Schaffer, C. B.

Shapiro, E. A.

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

Shapiro, M.

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

E. A. Shapiro, V. Milner, and M. Shapiro, “Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Theory,” Phys. Rev. A 79, 023422 (2009).
[Crossref]

A. A. Rangelov and N. V. Vitanov, “Complete population transfer in a three-state quantum system by a train of pairs of coincident pulses,” Phys. Rev. A 85, 043407 (2012).
[Crossref]

Figures (5)

Beamprop simulation of transport in structures designed in table 1 in the (a) counter intuitive and (b) intuitive directions. Images are taken at the y = 0 slice. In the counter-intuitive scheme, the small populations in the intermediate guides make the design tolerant to scattering losses from improper segment length, conversely the very high population in the intuitive direction makes these highly sensitive devices. Spaces of 2.5mm where added between waveguidelets to highlight digitisation.

(Left) Schematic of device with parameters determined by Table 1. (Right) Stitched differential interference contrast (DIC) microscope image of the start and end of a waveguidelet making up the dark state. A taper and a void are evident at either end.

Characterisation at 808 nm. The contrast ratio is plotted as Pc/(Pa + Pc) for the counter-intuitive configuration (a). The total transmission is also plotted as (Pa + Pc)/Pref, for the counter-intuitive configuration (b) and the intuitive configuration (c). Insets show a CCD image of the voids at the end of the waveguidelets. The voids are shown to be bright and strongly scattering in the intuitive configuration, but dark in the counter-intuitive configuration where they remain largely unpopulated. Transmission is higher in the backwards direction in almost all cases. Mean (solid line) and standard deviation (dashed) have been indicated.

Spectral response of the devices are plotted, measured in the forwards direction. (a) Counter-intuitive contrast ratio plotted as Pc/(Pa + Pc), and (b) the intuitive transmission plotted as (Pa + Pc)/Pref. Note that the optimal operating wavelength is shifted from 800 nm (dashed) to be about 830 nm (shaded). It can be seen that the broad wavelength response in the counter-intuitive configuration coincides with a suppressed response in the intuitive configuration.

Second set of measurements taken of waveguide written at 30.5nJ, using bandpass filtering. (a) Contrast ratio Pa/(Pa + Pc) as a function of wavelength. Shaded area corresponds to 95% confidence interval using bisquare method. The fitted equation is cos2(2π(λ − λopt)/λλ) where λopt = 823.00 ± 0.17 nm and λλ = 541.15 ± 1.39 nm. (b) Device transmission (Pa + Pc)/Pref as a function of wavelength. A section of the transmission around 805 nm has been omitted due to a normalisation error. In the optimum region, transmission typically lies between 75% to 95% (shaded in-image)

Tables (1)

Table 1 Device parameters used in all calculations herein. All waveguidelets are aligned at y = 0 and |a〉, |b〉1, |c〉 all begin at z = 0. The waveguide’s center is given by x. All waveguidelet pairs |b〉i+1 and |b〉i are separated in z by 7.5 mm to increase the total length to 70 mm to further demonstrate digitisation. ρ is the 1/e length of the Gaussian profile waveguides and δ is the difference between core and cladding indices. For details about the model parameters see [19].

Metrics

Table 1

Device parameters used in all calculations herein. All waveguidelets are aligned at y = 0 and |a〉, |b〉1, |c〉 all begin at z = 0. The waveguide’s center is given by x. All waveguidelet pairs |b〉i+1 and |b〉i are separated in z by 7.5 mm to increase the total length to 70 mm to further demonstrate digitisation. ρ is the 1/e length of the Gaussian profile waveguides and δ is the difference between core and cladding indices. For details about the model parameters see [19].